As one example, a conventional noise suppression device suppresses a noise component using: a main signal where a target sound and a noise are mixed; and a noise reference signal (see Patent Literature 1, for example).
A noise suppression device (a microphone device) disclosed in Patent Literature 1 detects a state where only a noise desired to be suppressed is present, according to a level determination or the like. Then, the noise suppression device estimates a power spectrum of the noise included in a main signal, based on an average power spectrum ratio between the main signal and a noise reference signal and on a power spectrum of the noise reference signal.
Following this, a filter coefficient for suppressing an estimated noise component is determined, and filtering is performed on the main signal to suppress the noise component. Hereinafter, the technique disclosed in Patent Literature 1 to suppress the noise component may also be referred to as the conventional technique A.